Laminated supports or flexible bearings are made up of layers of rigid material or "reinforcement" alternating with layers of resiliently deformable material, typically rubber or elastomer, which layers adhere securely to the reinforcement. Such flexible bearings are characterized by high strength against compression forces exerted perpendicularly to the layers, and by a relatively high capacity for resilient deformation in shear parallel to the layers.
A particular field of application for the invention is laminated spherical flexible bearings as used for forming joints between parts that may pivot relative to each other through a small angle about a pivot center. In laminated spherical flexible bearings, the reinforcement and the layers of rubber have surfaces in the form of spherical zones.
As particular examples of possibilities on which laminated spherical flexible bearings are used, mention may be made of the joints connecting an up duct to a submarine well-head, or the joints connecting a nozzle to a rocket body.
For example, with laminated flexible bearings for a nozzle, proposals have been made to replace the traditionally metal reinforcement with reinforcement made of composite material enabling a significant mass saving to be obtained while still providing very good mechanical performance under the conditions in which such nozzles are used. A particular material constituting such reinforcement is carbon-epoxy, i.e. a material constituted by carbon fiber reinforcement embedded in a matrix of epoxy resin.
A method currently used by the Applicant of the present application for making carbon-epoxy spherical composite reinforcements, consists in draping and molding layers of carbon cloth that have been pre-impregnated with epoxy resin. More precisely, the method comprises the following steps:
cutting out layers in the form of annular sectors 2 from pre-impregnated carbon cloth 1, the shape of the sectors being close to that of developed truncated cones FIG. 1);
draping the pre-impregnated layers of cloth in a rosette pattern on a male mold 3 having a surface in the form of a spherical zone corresponding to the inside surface of the spherical reinforcement to be made (FIGS. 2 and 3);
compacting the layers in a vacuum by means of a membrane;
installing them in a female mold 4 having a surface in the form of a spherical zone corresponding to the outside surface of the reinforcement to be made (FIG. 4);
polymerizing the assembly while under pressure; and
demolding the reinforcement.
The above method is very difficult to implement: it includes steps that must be performed manually and that require know-how and skills.
In addition, while being installed in the female mold, the layers may slide, thereby giving rise to folds (faults) and changing the distribution of the reinforcing fibers between the larger diameter and the smaller diameter of the reinforcement.
Furthermore, after demolding, the effect of releasing internal stresses can cause deformation in the reinforcement which can be detected only by inspection that is thorough.
With that method, it is also difficult to obtain reinforcement of varying thickness even though that can be desirable in some cases, particularly for increasing the mechanical strength of a flexible bearing in the vicinity of its small diameter where the largest forces are applied.
An object of the present invention is thus to provide a method of making laminated flexible bearings while avoiding the above drawbacks, i.e. a method that is simpler to implement and that avoids creating faults in reinforcement while making it possible to provide reinforcement of varying thickness.